Bedroom athletics may not be necessary to reap health benefits from sexual activity, researchers suggest.

Even non-vigorous sex may be enough to significantly reduce the risk of heart attack and stroke.

Even mild to moderate levels of physical activity are likely to have some cardiovascular protective effect

Professor Shah Ebrahim, Univeristy of Bristol

The research, based on a large number of men living in a South Wales town, also provides encouragement to those who can only manage mild or moderate levels of any sort of exercise.

The Caerphilly study, the results of which were presented at the World Stroke Congress in Melbourne, found that men having three or four orgasms a week actually halved the risk of having a major heart attack or stroke.

Previous research suggested that exercise had to involve a significant rise in heart rate over a sustained period to be of benefit.

It was thought that the exercise should at least leave the person out of breath, to be of use.

Regular exercise strengthens the heart muscle, which means it does not have to work so hard in normal situations.

Moderate activity

The University of Bristol researchers interviewed 2,400 men from the town, asking them how often they had sex.

They were then tracked 10 years later to see how many had suffered serious strokes and heart attacks.

Lead researcher Professor Shah Ebrahim said: "In the past we thought it had to be activity at least three times a week and lasting 20 minutes or longer, causing sweatiness and being out of breath.

"That's quite vigorous activity. Most men of course think it's sex, which most women think lasts only a few minutes and isn't nearly as sustained as that."

He said: "We're now moving to a situation where we would say that even mild to moderate levels of physical activity are likely to have some cardiovascular protective effect."

While doctors do not recommend strenuous exercise following a heart attack, mild to moderate exercise can be beneficial, and they have moved to reassure patients worried about making love for fear of triggering another attack.

Three week recovery

Alison Shaw, a cardiac nurse at the British Heart Foundation, said that, on average, sexual activity could resume only a few weeks after an attack, provided the patient was capable of walking a few hundred yards or climbing a flight of steps without getting out of breath or suffering chest pain.

She said: "The risk of suffering a heart attack during sex is very small."

In general, she recommended that people should take at least 30 minutes exercise five days a week, although this could be a brisk walk if necessary.

She said: "People are under the impression that it has to be strenuous exercise, but it doesn't."

The thousands of men taking part in the ongoing Caerphilly survey have, through their questionnaires, yielded vital clues to the relationship between diet and smoking and heart disease.

Unfaithful stroke victims

Two other pieces of research on strokes were presented at the World Stroke Congress, suggesting unusual risk factors for the condition.

Dr Izumi Toyoda, based in Tokyo, suggested that infidelity might leave men prone to the condition - 19 out of 42 people who had suffered strokes during sex were being unfaithful at the time.

And another paper found that the worst snorers also appeared to be at greater risk of strokes - a situation worsened by alcohol consumption.